1 /*
2  * Copyright (C) 2005,2006,2007,2008 IBM Corporation
3  *
4  * Authors:
5  * Serge Hallyn <serue@us.ibm.com>
6  * Reiner Sailer <sailer@watson.ibm.com>
7  * Mimi Zohar <zohar@us.ibm.com>
8  *
9  * This program is free software; you can redistribute it and/or
10  * modify it under the terms of the GNU General Public License as
11  * published by the Free Software Foundation, version 2 of the
12  * License.
13  *
14  * File: ima_queue.c
15  *       Implements queues that store template measurements and
16  *       maintains aggregate over the stored measurements
17  *       in the pre-configured TPM PCR (if available).
18  *       The measurement list is append-only. No entry is
19  *       ever removed or changed during the boot-cycle.
20  */
21 #include <linux/module.h>
22 #include <linux/rculist.h>
23 #include <linux/slab.h>
24 #include "ima.h"
25 
26 #define AUDIT_CAUSE_LEN_MAX 32
27 
28 LIST_HEAD(ima_measurements);	/* list of all measurements */
29 
30 /* key: inode (before secure-hashing a file) */
31 struct ima_h_table ima_htable = {
32 	.len = ATOMIC_LONG_INIT(0),
33 	.violations = ATOMIC_LONG_INIT(0),
34 	.queue[0 ... IMA_MEASURE_HTABLE_SIZE - 1] = HLIST_HEAD_INIT
35 };
36 
37 /* mutex protects atomicity of extending measurement list
38  * and extending the TPM PCR aggregate. Since tpm_extend can take
39  * long (and the tpm driver uses a mutex), we can't use the spinlock.
40  */
41 static DEFINE_MUTEX(ima_extend_list_mutex);
42 
43 /* lookup up the digest value in the hash table, and return the entry */
44 static struct ima_queue_entry *ima_lookup_digest_entry(u8 *digest_value)
45 {
46 	struct ima_queue_entry *qe, *ret = NULL;
47 	unsigned int key;
48 	int rc;
49 
50 	key = ima_hash_key(digest_value);
51 	rcu_read_lock();
52 	hlist_for_each_entry_rcu(qe, &ima_htable.queue[key], hnext) {
53 		rc = memcmp(qe->entry->digest, digest_value, TPM_DIGEST_SIZE);
54 		if (rc == 0) {
55 			ret = qe;
56 			break;
57 		}
58 	}
59 	rcu_read_unlock();
60 	return ret;
61 }
62 
63 /* ima_add_template_entry helper function:
64  * - Add template entry to measurement list and hash table.
65  *
66  * (Called with ima_extend_list_mutex held.)
67  */
68 static int ima_add_digest_entry(struct ima_template_entry *entry)
69 {
70 	struct ima_queue_entry *qe;
71 	unsigned int key;
72 
73 	qe = kmalloc(sizeof(*qe), GFP_KERNEL);
74 	if (qe == NULL) {
75 		pr_err("IMA: OUT OF MEMORY ERROR creating queue entry.\n");
76 		return -ENOMEM;
77 	}
78 	qe->entry = entry;
79 
80 	INIT_LIST_HEAD(&qe->later);
81 	list_add_tail_rcu(&qe->later, &ima_measurements);
82 
83 	atomic_long_inc(&ima_htable.len);
84 	key = ima_hash_key(entry->digest);
85 	hlist_add_head_rcu(&qe->hnext, &ima_htable.queue[key]);
86 	return 0;
87 }
88 
89 static int ima_pcr_extend(const u8 *hash)
90 {
91 	int result = 0;
92 
93 	if (!ima_used_chip)
94 		return result;
95 
96 	result = tpm_pcr_extend(TPM_ANY_NUM, CONFIG_IMA_MEASURE_PCR_IDX, hash);
97 	if (result != 0)
98 		pr_err("IMA: Error Communicating to TPM chip, result: %d\n",
99 		       result);
100 	return result;
101 }
102 
103 /* Add template entry to the measurement list and hash table,
104  * and extend the pcr.
105  */
106 int ima_add_template_entry(struct ima_template_entry *entry, int violation,
107 			   const char *op, struct inode *inode,
108 			   const unsigned char *filename)
109 {
110 	u8 digest[TPM_DIGEST_SIZE];
111 	const char *audit_cause = "hash_added";
112 	char tpm_audit_cause[AUDIT_CAUSE_LEN_MAX];
113 	int audit_info = 1;
114 	int result = 0, tpmresult = 0;
115 
116 	mutex_lock(&ima_extend_list_mutex);
117 	if (!violation) {
118 		memcpy(digest, entry->digest, sizeof digest);
119 		if (ima_lookup_digest_entry(digest)) {
120 			audit_cause = "hash_exists";
121 			result = -EEXIST;
122 			goto out;
123 		}
124 	}
125 
126 	result = ima_add_digest_entry(entry);
127 	if (result < 0) {
128 		audit_cause = "ENOMEM";
129 		audit_info = 0;
130 		goto out;
131 	}
132 
133 	if (violation)		/* invalidate pcr */
134 		memset(digest, 0xff, sizeof digest);
135 
136 	tpmresult = ima_pcr_extend(digest);
137 	if (tpmresult != 0) {
138 		snprintf(tpm_audit_cause, AUDIT_CAUSE_LEN_MAX, "TPM_error(%d)",
139 			 tpmresult);
140 		audit_cause = tpm_audit_cause;
141 		audit_info = 0;
142 	}
143 out:
144 	mutex_unlock(&ima_extend_list_mutex);
145 	integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
146 			    op, audit_cause, result, audit_info);
147 	return result;
148 }
149